This invention relates to gas-insulated substations, and more particularly relates to a novel arrangement to prevent the contamination of the main bus if there is a failure of auxiliary gas-filled equipment connected to the main bus.
High voltage gas-insulated substations are well known in which bus conductors, disconnecting switches, circuit breakers and other components are enclosed in leak-tight, grounded metal enclosures, and energized parts are insulated from ground by means of compressed SF.sub.6 gas. In such substations, buses are of concentric tubular construction as described, for example, in U.S. Pat. Nos. 3,573,341, 3,573,342 and 3,546,356.
In addition to circuit breakers and disconnecting switches, many gas-insulated substations require the addition of accessory equipment, such as surge arresters, potential transformers, capacitance voltage transformers and the like. These accessories are also mounted in grounded metal enclosures and surrounded by the compressed SF.sub.6, as described, for example, in U.S. Pat. No. 3,624,450 and in copending application Ser. No. 758,635, filed Jan. 12, 1977, now U.S. Pat. No. 4,130,850, in the name of John C. Cronin et al, entitled HIGH SPEED FAULT DIVERTER SWITCH FOR GAS-INSULATED SYSTEMS, and assigned to the assignee of the present invention.
In gas-insulated substations now in service, these accessories are directly connected to the gas-insulated bus without any gas barrier between the accessory and the bus. Accessories such as arresters, coupling capacitors and potential transformers can and do occasionally fail; when they do, the amount of energy available in a high voltage station is sufficient to cause an internal explosion, involving high pressures and very high temperatures. If such failure occurred in an accessory directly connected to a main substation bus, metallic particles and gases and other debris could be driven into the bus. The failure would, of course, cause circuit breakers to open and de-energize the accessory and the bus but, with metallic vapor condensed on the insulator surfaces and metal particles in the main bus, it would be impossible to re-energize the bus until it had been thoroughly cleaned. The cleaning of the bus would require dismantling and re-assembly of the bus, which would typically require at least several days.